1. Field of the Invention
The present invention is a tablet formulation which reduces the rate of precipitation of a rapidly precipitating drug and improves dissolution.
2. Description of the Related Art
U.S. Pat. No. 5,563,142 (EXAMPLE 105) discloses delavirdine.
International Publication WO95/28398 based on PCT patent application PCT/US95/02166 discloses delavirdine mesylate in two crystal forms “S” and “T”.
U.S. Pat. No. 5,358,941 discloses a compressed tablet formulation comprising about 0.5 to 40% active ingredient, about 10–80% anhydrous lactose, about 5 to 50% by weight of microcrystalline cellulose, about 0.5 to 10% by weight of croscarmallose sodium and about 0.1 to 5% magnesium stearate. The pharmaceutical tablet formulation of the present invention does not require lactose.
Patent EP 283925 discloses utilization of solvent-based polymers under action of high shearing forces so that precipitation is divided into smallest particles to purify resorbable polyester products. The claimed invention does not co-precipitate polymers in any solvent system with the rapidly precipitating drug prior to formulation with other ingredients, but relies only on close proximity of the dry binder or superdisintegrant with the rapidly precipitating drug in a conventional compressed tablet dosage form.
International Journal of Pharmaceutics, 154, 59–66 (1997) discloses the utilization of HPMC, HPC and PVP in a liquid system at various polymer ratios with intent to delay precipitation. Methods discussed include preparation of solid dispersions either by the co-precipitation method of grinding method to improve dissolution properties. The claimed invention utilizes conventional direct compression method of tablet formulation and does not utilize any solid dispersion techniques such as co-precipitation via solvent use or grinding to achieve co-precipitation.
The Handbook of Drug Excipients, 2nd. Ed., edited by A. Wade and P. J. Weller. 1994, page 141, and many other pharmaceutical references, describe the common use of superdisintegrants such as croscarmellose sodium are used to aid tablet disintegration typically in the amount of 1–2% and not more than 5% of the formulation. Higher amounts are not used or recommended due to gelation of the croscarmellose sodium forming a loose matrix which is known to impede dissolution of many drug compounds. The present invention uses greater than 6% croscarmellose sodium.
The Handbook of Drug Excipients, 2nd. Ed., edited by A. Wade and P. J. Weller. 1994, pages 223, 229 and 392, and many other pharmaceutical references, describe the common use of water soluble polymers such as HPMC, HPC-L, and PVP as binders, either as wet binders or dry binders, in immediate and sustained release tablet formulations. For non-sustained release applications, not more than 5% is used of these binders. Higher amounts are not recommended due to impedance of the dissolution rate for many drugs. Amounts higher than 5% of especially HPMC are commonly used only for sustained release dosage forms, and are generally of high molecular weight grades. In the present invention, however, the binder includes use at levels of greater than 5%.
U.S. Pat. No. 5,225,197 discloses a chewable tablet formulation. The present invention is not a chewable tablet.
JP 84-185584 discloses the utilization of HPC, PVP and other binders together with difficulty soluble drugs by use of heat. The claimed invention does not use heat.